JP2008181639A - Optical disc device, optical information device including optical disc device, and focus pull-in control LSI provided in optical disc device - Google Patents

Abstract

Even in an optical disk apparatus in which the WD of an objective lens is set narrow due to the high density and thinning of the optical disk, the influence of the surface shake of the optical disk is removed, and the focus servo is pulled in without the objective lens colliding with the optical disk. Provided is an optical disc device that can be used.
When a focus is pulled into an information recording surface 1b of a disk 1, a focus servo is first pulled into a substrate surface 1a of the disk 1, and a drive signal necessary for tracking the surface runout is stored in a state where the servo is set. Based on the signal obtained by superimposing this signal and the focus search drive signal, the focus is drawn into the information recording surface 1b of the disc 1.
[Selection] Figure 1

Description

  The present invention relates to an optical disk apparatus that optically records a signal on an optical disk using a light source such as a laser or reproduces a signal from the optical disk, and more particularly to an optical disk apparatus that performs focus control for controlling the focus of a light beam. Furthermore, the present invention relates to an optical information device provided with such an optical disk device, and a focus pull-in control LSI provided in the optical disk device.

  In order to optically record and reproduce information on an information carrier using a light source such as a laser, it is necessary to perform focus control so that the information recording surface of the optical disk is always at the focus (convergence point) position of the light beam. There is. In order to realize this, a so-called focus pull-in operation is performed in which the objective lens is moved to bring the focal position of the light beam to the information recording surface of the optical disc before focus control.

  Further, in recent optical disc apparatuses, it is necessary to shorten the distance between the optical disc and the objective lens, so-called working distance (hereinafter also abbreviated as WD), because of demands for large capacity and thinning.

  First, in order to reduce the thickness of the device, it is most effective to reduce the WD of the objective lens. This is because if the objective lens WD is made small, not only the optical disk / lens distance can be shortened, but also the lens aperture can be made smaller and the rising mirror diameter can be made smaller than the reduction amount of WD itself. This is because a much larger thickness can be achieved.

  Further, in order to increase the capacity, it is necessary to increase the resolution limit in order to increase the recording density. For this purpose, it is necessary to increase the numerical aperture of the objective lens. As a result, WD becomes very small.

  As a result, in the conventional optical disk apparatus, there has been a risk that the objective lens may collide with the surface of the optical disk substrate due to surface wobbling of the optical disk during the focus pull-in operation, and damage the optical disk or the lens system.

  Therefore, various measures have been devised to solve the collision during the focus pull-in operation.

  For example, the conventional optical disk device shown in Patent Document 1 is provided with a non-contact sensor capable of detecting the vertical movement vibration of the optical disk, and the objective lens gradually approaches the optical disk while performing almost the same movement as the optical disk vertical movement. As described above, the focus search is performed by driving the objective lens actuator. Thereby, even when the WD is narrow, it is possible to realize focus pull-in without causing a collision between the objective lens and the disk.

Further, the conventional optical disk apparatus disclosed in Patent Document 2 is designed to bring the focus servo to the surface of the optical disk substrate and then jump control the objective lens to the information recording surface once the focus servo is pulled into the surface of the optical disk substrate. Pull in the focus servo. As a result, the distance corresponding to the thickness of the base material of the optical disk can be increased as the working distance margin when the focus servo is pulled in, and collision between the objective lens and the recording medium can be prevented when the focus servo is pulled in.
JP 2003-91833 A Japanese Patent Laid-Open No. 2002-230792

  However, according to Patent Document 1, it is necessary to separately provide a non-contact sensor in the optical head device, which increases the cost and decreases the merchantability of the product.

  Further, the non-contact sensor needs to be installed at a position away from the objective lens, and causes a surface shake amount detection error due to a deviation of the installation position. For example, if the position of the non-contact sensor is set several tens of millimeters away from the objective lens in the radial direction of the optical disk, the error is about 150 μm with respect to the surface shake amount of 300 μm. Alternatively, if the position of the non-contact sensor is set several tens of millimeters away from the objective lens in the tangential direction of the optical disc, the maximum amplitude of the surface deflection of the optical disc can be detected with almost no error, but the phase shift of the position variation period Occurs and the amount of phase shift is about 40 degrees. When this phase shift is converted to a position shift of the optical disc, it is about 90 μm when considered in the middle of the optical disc. Therefore, since the installation position of the non-contact sensor is away from the objective lens, the vertical motion detection error due to the surface deflection of the optical disk becomes large. Therefore, there is a possibility that the optical disk and the objective lens collide during the focus pull-in operation.

  Further, the non-contact sensor has a large variation in sensitivity due to variations in solids and mounting errors. As a result, the vertical motion detection error due to the surface deflection of the optical disc becomes large, and the optical disc and the objective lens may collide during the focus pull-in operation.

  According to Patent Document 2, after the focus servo is once drawn onto the surface of the optical disk substrate, the focus of the light beam is jumped to the information recording surface of the optical disk by a jump operation.

  Here, the relative speed between the disk and the lens at the time of servo switching is called the rush speed, and the speed range that does not exceed the focus detection range when the objective lens is decelerated at the maximum in the focus servo process is called the rush speed limit.

  When the focus servo process is switched, the retraction can be safely performed when the rush speed is within the rush speed limit depending on the focus error detection range.

  In the case of a normal optical disc, the focus error detection range is about 20 μm PP, whereas in a high-density two-layer disc or the like, the focus error detection range is limited to about 5 μm PP. Therefore, there is a risk that the rush speed limit will be exceeded even at a normal rotational speed.

  However, according to Patent Document 2, the relative speed between the disk and the lens immediately after switching to the jump operation must be a value obtained by adding at least the jump speed and the surface shake speed. In addition, in the jump operation, it is necessary to jump the distance corresponding to the air equivalent of the base material thickness of the optical disk. Therefore, since the jump distance is long, the relative speed may be further increased due to variations in sensitivity and power supply voltage of the objective lens actuator. Therefore, it is conceivable that the rush speed is increased in a device whose rush speed limit is reduced, and the rush speed easily exceeds the rush speed limit. As a result, there is a risk of scratching the disc and the objective lens due to the collision between the objective lens and the disc substrate surface.

  Further, when the focus pull-in fails due to the jump operation, the objective lens is in the shake range due to the surface shake of the optical disc, and the objective lens almost collides with the optical disc.

  The object of the present invention has been made in view of the above-described conventional problems, and even in an optical disk apparatus in which the WD of the objective lens is set narrower by increasing the density and thickness of the optical disk, the influence of the surface shake of the optical disk is removed. An optical disc apparatus capable of performing focus servo pull-in without collision between the objective lens and the optical disc, an optical information device including the optical disc device, and a focus pull-in control LSI provided in the optical disc device are provided. It is.

  The present invention provides an optical disc apparatus having the following configuration in order to solve the above technical problem.

According to the optical disc apparatus of the first aspect of the present invention, the objective lens and the objective lens actuator that moves the objective lens in a direction at least perpendicular to the optical disc are provided, and the objective lens is moved by moving the objective lens. An optical head device that converges and irradiates a light beam to the optical disc,
A focus error detection circuit that generates a focus error signal in accordance with the positional deviation of the focal point of the light beam with respect to the substrate surface or the information recording surface of the optical disc;
A focus control circuit that controls the objective lens actuator based on the focus error signal obtained by the focus error detection circuit to follow the focal position of the light beam on the substrate surface or the information recording surface;
A surface shake tracking signal storage device that stores a surface shake tracking signal that is a drive signal applied to the objective lens actuator when the focus position is made to follow the base material surface;
A focus search drive signal generating circuit for generating a focus search drive signal which is a drive signal for changing the focal position of the light beam with respect to the optical disc;
A superimposed signal generation circuit that generates a signal in which the surface shake tracking signal stored in the surface shake tracking signal storage device and the focus search drive signal generated by the focus search drive signal generation circuit are superimposed;
Focus that draws focus on the information recording surface of the optical disc by controlling the objective lens actuator based on the superimposed signal generated by the superimposed signal generating circuit after drawing the focus servo on the substrate surface of the optical disc And a pull-in control circuit.

According to the optical disc device of the second aspect of the present invention, the optical head device is a light source that emits light beams of a plurality of wavelengths or a plurality of light sources that emit light beams having different wavelengths in response to reproduction on a plurality of types of optical discs. It has
The focus pull-in control circuit uses the light beam having a focal length longer than the focal length of the objective lens in the light beam corresponding to the optical disc to be recorded / reproduced among the light beams of a plurality of wavelengths emitted from the light source. You may comprise so that a focus servo may be drawn in to the base-material surface of an optical disk.

According to the optical disk device of the third aspect of the present invention, the optical head device is a light source that emits light beams of a plurality of wavelengths or a plurality of light beams that emit different wavelengths in response to reproduction on a plurality of types of optical disks. A light source and a plurality of objective lenses;
The focus pull-in control circuit is a light having a focal length longer than the focal length of the objective lens in the light source and objective lens used corresponding to the optical disk to be recorded / reproduced among the light source and objective lens emitting the plurality of light beams. You may comprise so that a focus servo may be drawn in to the base-material surface of the said optical disk using the combination of the light source and objective lens which emit a beam.

  According to the optical disk device of the fourth aspect of the present invention, the light source that emits a light beam having a longer focal length of the objective lens may be configured to be a light source that emits red light or infrared light.

  According to the optical disc apparatus of the fifth aspect of the present invention, the focal length of the objective lens through which the light beam that increases the focal length of the objective lens passes is larger than the surface shake amount of the optical disc to be recorded and reproduced. You may do it.

  According to the optical disc device of the sixth aspect of the present invention, the focus pull-in control circuit corrects in advance a focus shift due to spherical aberration corresponding to the substrate thickness of the optical disc when the focus servo is drawn into the substrate surface of the optical disc. You may comprise so that a focus servo may be drawn in in the position which carried out.

According to the optical disc device of the seventh aspect of the present invention, the optical disc apparatus further includes a spherical aberration correction actuator that moves the collimator lens to correct the spherical aberration caused by the change in the substrate thickness of the optical disc,
The focus pull-in control circuit may be configured to shift the collimator lens in advance to a correction position that is positioned when the substrate thickness is the smallest when pulling focus servo onto the substrate surface of the optical disc.

  An optical information apparatus according to an eighth aspect of the present invention includes the optical disc apparatus according to any one of the first to seventh aspects, and an arithmetic unit that performs computation of information reproduced by the optical disc apparatus.

  Further, the focus pull-in control LSI according to the ninth aspect of the present invention reproduces at least information by moving the objective lens by the objective lens actuator in a direction at least perpendicular to the optical disc to converge the light beam on the optical disc. A focus error detection unit that generates a focus error signal corresponding to a positional deviation of a focal point of a light beam with respect to a base material surface or an information recording surface of the optical disk, and the focus error obtained by the focus error detection unit. A focus control unit that causes the focal position of the light beam to follow the substrate surface or the information recording surface based on a signal, and a drive that is applied to the objective lens actuator when the focal position follows the substrate surface Surface run-out tracking signal storage unit that stores surface run-out tracking signal A focus search drive signal generating unit that generates a focus search drive signal that is a drive signal for changing the focal position of the light beam with respect to the optical disc, and the surface shake stored in the surface shake follow-up signal storage unit A superimposition signal generator for generating a signal obtained by superimposing the follow-up signal and the focus search drive signal generated by the focus search drive signal generator; and after the focus servo is drawn into the substrate surface of the optical disc, the superimposed signal A focus pull-in control unit that performs focus pull-in on the information recording surface of the optical disc based on the superimposed signal generated by the generation unit.

  According to the first aspect of the present invention, when the focus is pulled into the information recording surface of the optical disc, the focus servo is first drawn into the substrate surface of the optical disc, and the drive signal necessary for tracking the surface runout with the servo set is obtained. A certain surface shake tracking signal is stored, and focus pull-in to the information recording surface of the optical disc is performed based on a signal obtained by superimposing the surface shake tracking signal and the focus search drive signal.

  Therefore, it uses the light beam for reading or writing information to place the focus servo on the surface of the optical disk substrate, and detects vertical movement due to optical disk surface shake, eliminating the need for a separate non-contact sensor and increasing costs by adding components. There is no.

  Further, since the light beam for detecting the vertical movement of the optical disk is emitted from the objective lens itself, no surface shake amount detection error occurs and, of course, no phase deviation of the surface shake occurs.

  Further, since the distance from the optical disk by the light beam for reading or writing information is accurately detected by the focus error detection circuit mounted on the optical head device, no surface shake amount detection error occurs.

  Next, after the focus servo state is set on the surface of the optical disk substrate, a surface shake tracking signal which is a drive signal for tracking the surface shake is stored, and based on a signal obtained by superimposing the surface shake tracking signal and the focus search drive signal. The focus search operation is performed on the information recording surface of the optical disc. Therefore, the relative speed between the objective lens and the optical disc information recording surface is only the focus search operation excluding the vertical fluctuation due to the surface deflection of the optical disc. Therefore, the rush speed does not exceed the rush speed limit due to the focus pull-in.

  As a result, in the focus pull-in operation, the objective lens and the optical disk do not collide, and the optical disk apparatus with high reliability and low cost that does not damage the optical disk and the objective lens can be realized.

  According to the second aspect of the present invention, since the focal length of the objective lens is set longer, there is a possibility that the objective lens and the optical disc collide when the focus servo is drawn into the substrate surface of the optical disc. It can be further reduced.

  According to the third aspect of the present invention, for a recordable optical disc apparatus equipped with an optical head device in which a plurality of objective lenses suitable for a recordable optical head device requiring higher reliability are mounted on an objective lens actuator. Thus, when the focus servo is pulled in, the possibility that the objective lens and the optical disc collide with each other can be reduced, and the reliability of the apparatus can be increased and the merchantability of the product can be improved.

  According to the fourth aspect of the present invention, the operation of drawing the optical disk onto the substrate surface can be suitably performed using the light source that emits red light or infrared light.

According to the fifth aspect of the present invention, it is possible to realize a focus pull-in operation to the substrate surface of the optical disc without the objective lens entering the range of vertical movement of the optical disc due to the surface deflection of the optical disc. Therefore, the possibility that the objective lens and the optical disk collide can be further reduced.

  According to the sixth aspect of the present invention, an accurate and stable focus pull-in operation can be performed on the surface of the base material of the optical disc without reducing the margin of the focus error detection range.

  According to the seventh aspect of the present invention, by correcting the spherical aberration corresponding to the substrate thickness of the optical disc, the positional deviation of the focus of the light beam due to the spherical aberration is suppressed, and the surface of the substrate of the optical disc is more accurate and stable. The focus can be pulled in.

The optical disc apparatus according to the first to seventh aspects can be suitably used for various optical information devices such as computers, optical disc players, car navigation systems, optical disc recorders, and optical disc servers.
In addition, in the optical disc apparatus of the first to seventh aspects, the circuit portion for executing the focus pull-in control operation is manufactured by LSI, so that the optical disc apparatus can be reduced in size and thickness.

(Embodiment 1)
Hereinafter, an optical disc apparatus according to Embodiment 1 of the present invention will be described with reference to the drawings. In each figure, the same or similar components are denoted by the same reference numerals.

  FIG. 1 is a block diagram showing the configuration of the optical disk device according to the first embodiment, FIG. 2 is a schematic diagram showing the configuration of the optical head device provided in the optical disk device, and FIG. 3 shows the drawing process of the optical disk device according to the first embodiment. FIG. 4A is a flow chart illustrating a sequence, FIG. 4A is a schematic diagram showing the positional relationship between the optical disk and the objective lens in the focus servo state on the disk substrate surface in the optical disk apparatus according to the first embodiment, and FIG. FIG. 5 is a schematic diagram showing the positional relationship between the optical disk and the objective lens in a focus servo state on the disk information recording surface in the optical disk apparatus, and FIG. 5 shows the movement of the optical disk and the objective lens when the focus is pulled in the optical disk apparatus according to the first embodiment. It is a time chart which shows.

  As shown in FIG. 1, the optical disk apparatus of this embodiment is roughly divided into a spindle motor 2, an optical head device 3, an actuator drive circuit 8, an aberration corrector drive circuit 9, a spindle motor drive circuit 10, A focus error detection circuit 11, a focus control circuit 12, a surface shake follow-up signal storage device 13, a focus search drive signal generation circuit 14, a superimposed signal generation circuit 15, and a focus pull-in control circuit 16 are provided. The optical head device 3 roughly includes an objective lens 4, an optical system 5 including a light source and a photodetector, an objective lens actuator 6, and a correction actuator 7.

Further, as shown in FIG. 1, a focus error detection circuit 11, a focus control circuit 12, a surface shake follow-up signal storage device 13, a focus search drive signal generation circuit 14, a superimposed signal generation circuit 15, and a focus pull-in control. In this embodiment, the portion 50 including the circuit 16 is configured by an integrated circuit and is contained in one chip.
The optical disk apparatus of the present embodiment having the above configuration will be described in detail below.

  1 and 2, a disk 1 is an optical disk loaded in the optical disk apparatus of the present embodiment, and is chucked by a spindle motor 2 with a disk substrate surface 1a facing downward and has an information recording surface 1b. The optical head device 3 is disposed under the disk 1 and converges and irradiates the disk 1 with the light beam via the objective lens 4. In the present embodiment, the optical head device 3 has one objective lens 4.

  Here, the optical head device 3 will be described with reference to FIG. The thickness of the base material from the surface 1a of the optical disc 1 to the information recording surface 1b is referred to as the base material thickness. The optical head device 3 of the present embodiment is adapted for recording and reproduction of three types of optical discs 1 having a substrate thickness of 0.1 mm, 0.6 mm, and 1.2 mm, respectively, blue light having a wavelength of 405 nm and red light having a wavelength of 650 nm. Three types of laser light sources, light and infrared light of 780 nm, are mounted. The objective lens 4 is designed to be compatible so that light beams of three types of wavelengths are focused on the information recording surface 1b of each optical disc 1 having each substrate thickness.

  First, the collection of the blue light beam and the detection of the reflected light from the disk 1 will be described.

  The blue light beam 24 emitted from the blue laser 17, which is a blue light source, is reflected by the beam splitter 19 and the wedge beam splitter 20, and then becomes parallel light by the collimator lens 21 mounted on the spherical aberration actuator 7. Guided to the lens 4. The objective lens 4 focuses the blue light beam 24 on the information recording surface 1b of the disk 1 with a numerical aperture of 0.85, for example. Then, the light beam 24 is reflected by the information recording surface 1b of the disk 1, enters the objective lens 4 again, is reflected by the mirror 22, is transmitted through the collimator lens 21, and is reflected by the wedge beam splitter 20, and then the beam splitter. The light passes through 19 and enters the photodetector 23. The photodetector 23 detects the incident light, converts it into an electrical signal, and outputs it to the focus error detection circuit 11.

  On the other hand, a red light source that emits infrared laser light and an infrared light source that emits infrared laser light are incorporated in the two-wavelength unit 18. The infrared light beam 25 emitted from the two-wavelength unit 18 passes through the wedge beam splitter 20, becomes parallel light by the collimator lens 21, and is guided to the objective lens 4 by the mirror 22. Here, the infrared light beam 25 is described, but a red light beam (not shown) also passes through the same optical path. The objective lens 4 focuses on the information recording surface 1b of the disk 1 with a numerical aperture of 0.6 for red light beam and a numerical aperture of 0.45 for infrared light beam 25, for example. . The light beam 25 is reflected by the information recording surface 1 b of the disk 1, reenters the objective lens 4, is reflected by the mirror 22, passes through the collimator lens 21, passes through the wedge beam splitter 20, and then enters the two-wavelength unit 18. The light is incident on a photodetector incorporated in the. The photodetector in the two-wavelength unit 18 detects the incident light, converts it into an electrical signal, and outputs it to the focus error detection circuit 11.

  In the optical disk apparatus equipped with the optical head device 3 as described above, the objective lens actuator 6 drives the objective lens 4 in the vertical direction, that is, in the thickness direction of the loaded optical disk 1 by the drive signal from the actuator drive circuit 8. The focus of the light beam is positioned on the disk 1. Of course, the objective lens actuator drives the objective lens 4 also in the diameter direction of the disk 1 for tracking control. Further, the spherical aberration actuator 7 causes the spherical aberration caused by the variation in the substrate thickness of the disk 1 at the focal point formed by the objective lens 4 to move the collimator lens 21 in the direction of the arrow through the aberration correction actuator drive circuit 9. Correct by moving.

  The focus error detection circuit 11 is combined with the S-shaped waveform of the focus error signal obtained by calculating the signal obtained from the optical head device 3 by the reflected light reflected from the disk substrate surface 1a or the disk information recording surface 1b. The amount of error from the focus is detected and output.

  The focus control circuit 12 outputs a control signal for controlling the objective lens actuator 6 to the actuator drive circuit 8 so as to eliminate the error amount based on the focus error signal output from the focus error detection circuit 11.

  The surface shake follow-up signal storage device 13 monitors the drive signal of the actuator drive circuit 8 when the focus of the infrared light beam 25 is focused on the disk substrate surface 1a and the objective lens actuator 6 is in the focus servo state. In addition, it is stored as a follow-up signal for the surface shake of the disk 1.

  The focus search drive signal generation circuit 14 gradually moves the objective lens 4 closer to the disk 1 from a position sufficiently away from the surface shake range of the disk 1 in order to search for the S-shaped waveform output from the focus error detection circuit 11. Output a focus search drive signal.

  The superimposed signal generation circuit 15 outputs a superimposed signal in which the surface shake tracking signal output from the surface shake tracking signal storage device 13 and the focus search drive signal output from the focus search drive signal generation circuit 14 are superimposed.

  The focus pull-in control circuit 16 emits an infrared laser with the longest focal length of the objective lens 4 out of the three-wavelength light source when the disk 1 is a disk having a substrate thickness of 0.1 mm. The focus servo is pulled into the material surface 1a. Thereafter, the blue laser 17 is caused to emit light, and the optical disk device 3 is controlled so that the focus is drawn into the information recording surface 1 b of the disk 1 based on the superimposed signal output from the superimposed signal generation circuit 15.

  Next, the focus pull-in operation will be described with reference to FIGS.

  First, when the disk 1 having a substrate thickness of 0.1 mm is loaded into the spindle motor 2, an objective lens retract signal is output from the focus pull-in circuit 16 to the actuator drive circuit 8, and the objective lens is out of the surface deflection range of the disk 1. (FIG. 3, step S1). Thereafter, the spindle motor 2 is driven by the spindle motor drive circuit 10, and the disk 1 starts to rotate (FIG. 3, step S2).

  Next, the infrared laser of the two-wavelength unit 18 emits light, and an infrared light beam 25 of infrared light is emitted from the objective lens 4 to the optical disc 1 (FIG. 3, step S3). Here, the focus pull-in control circuit outputs the focus search drive signal from the focus search drive signal generation circuit 14 to the actuator drive circuit 8 to drive the objective lens actuator 6 (FIG. 3, step S5). As a result, the objective lens 4 is gradually brought closer to the disk 1, and the focus pull-in control circuit searches for the in-focus position between the base material surface 1a of the disk 1 and the focus of the infrared light beam 25 (FIG. 3, step S6). ). At this time, the spherical aberration correction actuator 7 moves the collimator lens 21 to a position where the base material is thinnest in the movable range of the collimator lens 21 (FIG. 3, step S4). When the in-focus position on the substrate surface 1a is detected by the focus error signal output from the focus error detection circuit 11, the focus pull-in control circuit 16 switches the drive of the objective lens actuator 6 to the focus control circuit 12 (FIG. 3). In step S7), the focus control circuit 12 is caused to perform focus servo on the substrate surface 1a of the disk 1 (FIG. 3, step S8).

  At this time, the relative positional relationship between the disk 1 and the objective lens 4 is as shown in FIG. 4A, and the infrared light beam 25 having the longest focal length is focused on the substrate surface 1a of the disk 1. Yes. Therefore, since the focal length is 2 mm or more, the relative distance between the disc 1 and the objective lens 4 is also 2 mm or more, which is sufficiently longer than the surface deflection range of the disc 1. Therefore, the disk 1 and the objective lens 4 do not collide at the time of drawing.

Here, the surface follow-up signal storage device 13 monitors the drive signal of the actuator drive circuit 8 and stores it as the surface shake follow-up signal of the disk 1 in association with the drive signal of the spindle motor drive circuit 10 (FIG. 3, step S9). . For example, a semiconductor memory or the like is used as the storage medium.
The superimposition signal generation circuit 15 performs focus pull-in control of a superimposition signal obtained by superimposing the surface shake tracking signal output from the surface shake tracking signal storage device 13 and the focus search drive signal output from the focus search drive signal generation circuit 14. It outputs to the circuit 16 (FIG. 3, step S10).
The focus pull-in control circuit 16 emits the blue laser 17 instead of the infrared light beam 25 in response to the supply of the superimposition signal (FIG. 3, step S11), and the superimposition signal output from the superimposition signal generation circuit 15 Is output to the actuator drive circuit 8 to search for the in-focus position between the information recording surface 1b of the disk 1 and the focal point of the blue light beam 24 (FIG. 3, steps S12 and S13). At this time, the spherical aberration correction actuator 7 moves the collimator lens 21 to a position corresponding to the spherical aberration correction corresponding to the base material thickness of 0.1 mm.
When the in-focus position with respect to the information recording surface 1b is detected by the focus error signal output from the focus error detection circuit 11, the focus pull-in control circuit 16 switches the drive control of the objective lens actuator 6 to the focus control circuit 12 (FIG. 3, Step S14). The focus control circuit 12 performs focus servo on the information recording surface 1b of the disk 1 and completes the focus pull-in operation.

  At this time, the relative positional relationship between the disk 1 and the objective lens 4 is as shown in FIG. 4B, and the blue light beam 24 is focused on the information recording surface 1 b of the disk 1. Therefore, although the WD is as short as 0.3 mm, for example, the objective lens 4 gradually reduces the relative distance from the disk 1 while vibrating in synchronism with the surface vibration of the disk 1 to perform the focus pull-in. And the objective lens 4 do not collide.

  The relative distance between the disk 1 and the objective lens 4 in the focus pull-in operation described above will be described with reference to FIG.

  In FIG. 5, first, the focus pull-in operation is started at time t0, and the objective lens 4 gradually approaches the disc 1 by the focus search operation to the base material surface 1a of the disc 1. At time t1, the in-focus position between the substrate surface 1a of the disk 1 and the focal point of the infrared light beam 25 is detected, and focus servo to the substrate surface 1a of the disk 1 is started. At this time, the objective lens 4 is located outside the surface deflection range of the disk 1 as described above, and safety against collision is ensured.

  Next, from time t2, the objective lens 4 gradually reduces the relative distance from the disk 1 while vibrating in synchronism with the surface vibration of the disk 1 by the superimposed signal, and performs focus pull-in. Therefore, the disk 1 and the objective lens 4 do not collide when the focus is pulled.

  At the time t3, the in-focus position between the focal point of the blue light beam 24 and the information recording surface 1b of the disk 1 is detected, and the focus pull-in control circuit 16 switches the drive control of the objective lens actuator 6 to the focus control circuit 12 to perform focus control. The circuit 12 performs focus servo on the information recording surface 1b of the disk 1 and completes the focus pull-in operation.

  As described above, according to the first embodiment of the present invention, when the focus is pulled into the information recording surface 1b of the disk 1, first, the focus servo is pulled into the base material surface 1a of the disk 1 to A surface shake tracking signal, which is a drive signal necessary for surface shake tracking when the focus servo is set, is stored. Based on a signal obtained by superimposing the surface shake follow-up signal and the focus search drive signal, focus pull-in to the information recording surface 1b of the disk 1 is performed.

  Therefore, in the present embodiment, a focus servo state is set on the substrate surface 1a of the disk 1 using a light beam for reading or writing information, and the vertical movement due to the surface shake of the disk 1 is detected. There is no need to install and there is no cost increase by adding parts

  Further, since the light beam for detecting the vertical movement due to the surface shake of the disk 1 is emitted from the objective lens 4 itself, no surface shake amount detection error occurs, and of course no phase deviation of the surface shake occurs.

  Further, the distance detection with the optical disc 1 by the light beam for reading or writing information is accurately detected by the focus error detection means mounted on the optical disc apparatus, so that no surface shake amount detection error occurs.

  Next, after a focus servo state is set on the disk substrate surface 1a, a drive signal for surface shake tracking is stored, and information recording on the optical disk is performed based on a signal obtained by superimposing the surface shake tracking signal and the focus search drive signal. A focus search operation is performed on the surface 1b. Therefore, the relative speed between the objective lens 4 and the disc information recording surface 1b is only the focus search operation excluding the vertical fluctuation due to the surface shake of the optical disc 1. Therefore, the rush speed does not exceed the rush speed limit in focus pull-in.

  As a result, the objective lens 4 and the disk 1 do not collide during the focus pull-in operation, and the disk 1 and the objective lens 4 are not damaged. Therefore, it is possible to realize an optical disc apparatus that is highly reliable and inexpensive.

  Further, when the focus is once drawn into the substrate surface 1a of the disk 1 having a substrate thickness of 0.1 mm corresponding to the blue light beam 24, the focus servo is performed using the infrared light beam 25. Therefore, among the three types of light beams that are compatible with the optical head device 3, the focal length of the objective lens 4 is the longest, and due to the long focal length, the distance from the disc 1 to the objective lens 4 is This is far enough from the range of vertical movement of the disk 1 due to surface runout. Therefore, it is possible to further eliminate the possibility that the objective lens 4 and the disk 1 collide with each other during the drawing into the substrate surface 1b.

  Further, since the spherical aberration correction actuator 7 moves the collimator lens 21 to the position where the base material is thinnest in the movable range of the collimator lens 21, the focus error signal due to the spherical aberration corresponding to the base material thickness of 1.2 mm. Deviation can be minimized, and stable focus pull-in and focus servo to the substrate surface 1a can be performed. When the focus is pulled into the information recording surface 1b, the spherical aberration correction actuator 7 moves the collimator lens 21 to a position corresponding to the spherical aberration correction corresponding to the base material thickness of 0.1 mm, so that stable focus pull-in is performed. Is possible.

  Further, when the focus is pulled into the substrate surface 1a, the focus is pulled in at a position where the focus shift due to the spherical aberration corresponding to the substrate thickness of 1.2 mm is corrected in advance, instead of driving the spherical aberration correcting actuator 7 in advance. May be.

  In the present embodiment, focus servo is once performed on the substrate surface with infrared light using an objective lens corresponding to three types of wavelengths, and then the focus is drawn into the information recording surface with blue light. Using two kinds of wavelengths or objective lenses corresponding to one kind of wavelength, in the case of two kinds, a light source having a longer wavelength is used. In the case of one kind, the focus servo is temporarily performed on the substrate surface by the light source. However, the present invention is not limited to this embodiment.

  In this embodiment, the focus pull-in control circuit controls the focus pull-in operation. However, it is sufficient that the controller has a similar function. For example, a part of the system controller may have the same function. Good.

(Embodiment 2)
Hereinafter, an optical disc apparatus according to Embodiment 2 of the present invention will be described with reference to the drawings.

  6 is a block diagram showing the configuration of the optical disk device according to the second embodiment, FIG. 7 is a schematic diagram showing the configuration of the optical head device of the optical disk device according to the second embodiment, and FIG. 8 is the diagram of the optical disk device according to the second embodiment. FIG. 9A is a schematic diagram showing the positional relationship between the optical disk and the objective lens in the focus servo state on the disk base material surface of the optical disk apparatus according to Embodiment 2, and FIG. 9B is the embodiment. 2 is a schematic diagram showing a positional relationship between an optical disc and an objective lens in a focus servo state on a disc information recording surface of the optical disc apparatus according to FIG.

  6 differs from FIG. 1 in that the optical head device 3 including the objective lens 4 has an optical head device 3 including two objective lenses 4a and 4b and optical systems 5a and 5b corresponding to the objective lenses 4a and 4b. The optical head device 30 is replaced. Other configurations are the same as those shown in FIG. 1, and components having similar functions are indicated by the same symbols.

  Accordingly, only the optical head device 30 will be described here with reference to FIG.

  The optical head device 30 according to the present embodiment has blue light with a wavelength of 405 nm and red light with a wavelength of 650 nm in order to cope with recording and reproduction of three types of discs having a substrate thickness of 0.1 mm, 0.6 mm, and 1.2 mm. , Three types of laser light sources of infrared light of 780 nm are mounted, and the objective lens 4a supports only the blue light beam and focuses on the information recording surface 1b of the disk 1 having a substrate thickness of 0.1 mm. Designed to tie. The objective lens 4b is designed to be compatible so that light beams of two types of wavelengths, red and infrared, are focused on the information recording surface 1b of the disk 1 having base material thicknesses of 0.6 mm and 1.2 mm.

  First, the collection of the blue light beam and the detection of the reflected light from the disk will be described.

  The blue light beam 24 emitted from the blue laser 17 that is a blue light source is reflected by the beam splitter 19, then becomes parallel light by the collimator lens 21 mounted on the spherical aberration actuator 7, and is guided to the objective lens 4 a by the mirror 22. . The objective lens 4a focuses the blue light beam 24 on the information recording surface 1b of the disk 1 with a numerical aperture of 0.85, for example. The light beam 24 is reflected by the information recording surface 1 b of the disk 1, is incident on the objective lens 4 a again, is reflected by the mirror 22, is transmitted through the collimator lens 21, is reflected by the beam splitter 19, and is incident on the photodetector 23. . The photodetector 23 detects the incident light, converts it into an electrical signal, and outputs it to the focus error detection circuit 11.

  On the other hand, an infrared light source that emits an infrared laser is incorporated in the infrared unit 18 b, and the infrared light beam 25 emitted from the infrared unit 18 b passes through the wedge beam splitter 20 and is collimated by the collimator lens 37. Thus, the light is guided to the objective lens 4b by the mirror 22. The objective lens 4b condenses the infrared light beam 25 on the information recording surface 1b with a numerical aperture of 0.45, for example. The light beam 25 is reflected by the information recording surface 1b of the disk 1, enters the objective lens 4b again, is reflected by the mirror 22, passes through the collimator lens 21, passes through the wedge beam splitter 20, and then passes through the infrared unit 18b. The light is incident on a photodetector incorporated in the. The photodetector detects incident light, converts it into an electrical signal, and outputs it to the focus error detection circuit 11.

  A red light source that emits red laser light is incorporated in the red unit 18a, and the red light beam 26 emitted from the red unit 18a is reflected by the wedge beam splitter 20 and then travels in the same optical path as the infrared light beam 25. Then, the light is again reflected by the wedge beam splitter 20 and incident on the photodetector incorporated in the red unit 18a. The photodetector detects incident light, converts it into an electrical signal, and outputs it to the focus error detection circuit 11.

  In the optical disk apparatus equipped with the optical head device 30 as described above, the objective lens actuator 6 drives the objective lenses 4 a and 4 b in the vertical direction by a drive signal from the actuator drive circuit 8 to focus the light beam on the disk 1. Positioning. Further, the spherical aberration actuator 7 corrects the spherical aberration caused by the variation in the substrate thickness of the disk 1 at the focal point formed by the objective lens 4a by moving the collimator lens 21 via the aberration correction actuator drive circuit 9. .

Next, the focus pull-in operation will be described with reference to FIGS. 8, 9A, and 9B. 8 differs from FIG. 3 in that the optical paths of the blue light beam and the infrared light beam are different, and therefore the step of moving the collimator lens 21 by the spherical aberration actuator, that is, step S4 shown in FIG. 3 is eliminated. 9A and 9B is different from FIGS. 4A and 4B in that the objective lens 4 has two objective lenses 4a and 4b.
The operation shown in FIG. 8 is the same as the operation shown in FIG. 3 except that step S4 is eliminated. Therefore, the description of the focus pull-in operation to the base material surface 1a and the information recording surface 1b of the optical disc 1 in the optical disc apparatus of Embodiment 2 is omitted here.

  Accordingly, the relative positional relationship between the disc 1 and the objective lenses 4a and 4b when the infrared light beam 25 is focused on the substrate surface 1a of the disc 1, and the blue light on the information recording surface 1b of the disc 1 The relative positional relationship between the disc 1 and the objective lenses 4a and 4b when the beam 24 is in focus will be described with reference to FIGS. 9A and 9B.

  When the focus of the infrared light beam 25 is focused on the substrate surface 1a of the disk 1 and focus servo is performed, the relative positional relationship between the disk 1 and the objective lenses 4a and 4b is as shown in FIG. 9A. The infrared light beam 25 having the longest focal length is focused on the substrate surface 1a of the disk 1 by the objective lens 4b. Therefore, the relative distance between the disc 1 and the objective lenses 4a and 4b is 2 mm or more, which is sufficiently longer than the surface deflection range of the disc 1. Therefore, the disc 1 and the objective lenses 4a and 4b do not collide when the focus is drawn into the substrate surface 1a.

  Further, when the focus of the blue light beam 24 is focused on the information recording surface 1b of the disk 1 to perform focus servo, the relative positional relationship between the disk 1 and the objective lenses 4a and 4b is as shown in FIG. 9B. Although the WD is as short as 0.3 mm, for example, the objective lenses 4a and 4b gradually reduce the relative distance from the disk 1 while vibrating in synchronization with the surface vibration of the disk 1 to perform focus pull-in. When the focus is pulled into the recording surface 1b, the disc 1 and the objective lenses 4a and 4b do not collide.

  As described above, in Embodiment 2 of the present invention, a recording-type optical disc equipped with an optical head device in which a plurality of objective lenses suitable for a recording-type optical head device requiring higher reliability is mounted on an objective lens actuator. When the focus servo is pulled into the apparatus, the possibility that the objective lens and the optical disk collide with each other can be reduced, the reliability of the apparatus can be increased, and the product quality of the product can be increased.

  Also, the optical disk device shown in FIG. 1 or FIG. 6 can be mounted on various devices. A computer, an optical disc player, and an optical disc recorder as optical information equipment equipped with the optical disc apparatus described in FIG. 1 or FIG. 6 can stably record or reproduce different types of optical discs, and can be used in a wide range of applications. FIG. 10 is a schematic diagram showing a configuration of a computer on which the optical disk device shown in FIGS. 1 and 6 is mounted.

  FIG. 10 shows a configuration example of a computer 470 as an example of an optical information device. 10, the optical disk device 350 shown in FIG. 1 or 6, the input device 471 such as a keyboard or mouse or touch panel for inputting information, the information input from the input device 471, the optical information device 350 An arithmetic unit 472 such as a central processing unit (CPU) that performs an operation based on information read from the output unit, and an output unit 473 such as a cathode ray tube, a liquid crystal display device, or a printer that displays information such as a result calculated by the arithmetic unit. The computer 470 provided with is configured.

  The computer 470 may be equipped with a wired or wireless input / output terminal that takes in information to be recorded on the optical disc 1 loaded in the optical disc device 350 or outputs information read out by the optical disc device 350 to the outside. As a result, information can be exchanged with a network, that is, a plurality of devices such as a computer, a telephone, a TV tuner, and the like, and the plurality of devices can be used as a shared information server (optical disk server). Since different types of optical discs can be stably recorded or reproduced, it has an effect that can be used for a wide range of purposes.

  Further, by providing a changer for taking a plurality of optical discs into and out of the optical disc apparatus 350, it is possible to obtain an effect that a large amount of information can be recorded / stored.

  FIG. 11A shows a schematic configuration of an optical disc player 480 as an example of an optical information device equipped with the optical disc device 350 shown in FIG. 1 or FIG. In FIG. 11A, an optical disc player 480 having an optical disc device 350 and an information-to-image conversion device (for example, a decoder 481) for converting an information signal obtained from the optical disc device 350 into an image is configured. This configuration can also be used as a car navigation system. In addition, a display device 482 such as a liquid crystal monitor may be added.

  FIG. 11B shows a schematic configuration of an optical disc recorder 490 as an example of an optical information device equipped with the optical disc apparatus 350 shown in FIG. 1 or FIG. 11B, an optical disc recorder 490 having the optical disc device 350 shown in FIG. 1 or 6 and an image-to-information conversion device (for example, an encoder 492) for converting image information into information to be recorded on the optical disc by the optical disc device 350. Constitute. Desirably, by mounting an information-to-image conversion device (decoder 491) for converting an information signal obtained from the optical disk device 350 into an image, the already recorded portion can be reproduced. An output device 493 such as a cathode ray tube or a liquid crystal display device for displaying information may be provided.

  In addition, in the apparatus using the optical disk device described in FIG. 1 or FIG. 6 described above, output devices are illustrated, but there is a product form in which an output terminal is mounted on these devices and the output device is configured separately. Needless to say, this is possible. In addition, although the input device is not illustrated in each of the above-described devices, a product form including an input device such as a keyboard, a touch panel, a mouse, and a remote control device is also possible. It is also possible to mount only.

  The optical disc apparatus according to the present invention can record and reproduce on a plurality of types of optical discs having different substrate thicknesses, corresponding wavelengths, recording densities, and the like. It is possible to handle optical discs of the following standards. Accordingly, the present invention can be applied to various systems that record and reproduce information, such as computers, optical disk players, optical disk recorders, car navigation systems, editing systems, optical disk servers, and AV components.

1 is a block diagram showing a configuration of an optical disc device according to a first embodiment. Schematic diagram showing the configuration of the optical head device of the optical disk device according to the first embodiment. 8 is a flowchart illustrating an example of a pull-in process sequence of the optical disc device according to the first embodiment. FIG. 3 is a schematic diagram showing a positional relationship between an optical disk and an objective lens in a focus servo state with respect to a disk substrate surface of the optical disk apparatus according to the first embodiment. FIG. 3 is a schematic diagram showing a positional relationship between an optical disc and an objective lens in a focus servo state on a disc information recording surface of the optical disc apparatus according to the first embodiment. Time chart showing movement of optical disc and objective lens at the time of focus pull-in according to Embodiment 1 FIG. 3 is a block diagram showing a configuration of an optical disc device according to a second embodiment. Schematic diagram showing the configuration of the optical head device of the optical disk device according to the second embodiment. 8 is a flowchart illustrating an example of a pull-in process sequence of an optical disc device according to the second embodiment Schematic diagram showing the positional relationship between the optical disk and the objective lens in the focus servo state on the disk substrate surface of the optical disk apparatus according to the second embodiment. Schematic diagram showing the positional relationship between the optical disc and the objective lens in a focus servo state on the disc information recording surface of the optical disc apparatus according to the second embodiment. Schematic diagram showing the configuration of a computer equipped with the optical disk device of FIG. 1 or FIG. The figure which shows schematic structure of the optical disk player carrying the optical disk apparatus shown in FIG. 1 or FIG. The figure which shows schematic structure of the optical disk recorder carrying the optical disk apparatus shown in FIG. 1 or FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Disc 1a Base material surface 1b Information recording surface 2 Spindle motor 3 Optical head device 4 Objective lens 6 Objective lens actuator 7 Spherical aberration actuator 8 Actuator drive circuit 9 Aberration corrector drive circuit 10 Spindle motor drive circuit 11 Focus error detection circuit 12 Focus Control circuit 13 Surface shake tracking signal storage device 14 Focus search drive signal generation circuit 15 Superimposition signal generation circuit 16 Focus pull-in control circuit 17 Blue laser 18 Two-wavelength unit 19 Beam splitter 20 Wedge beam splitter 21 Collimator lens 22 Mirror 23 Photo detector 24 Blue light Beam 25 Infrared light beam

Claims (9)

An optical head having an objective lens and an objective lens actuator that moves the objective lens in a direction at least perpendicular to the optical disc, and that converges and irradiates the optical disc with the objective lens by moving the objective lens Equipment,
A focus error detection circuit that generates a focus error signal in accordance with the positional deviation of the focal point of the light beam with respect to the substrate surface or the information recording surface of the optical disc;
A focus control circuit that controls the objective lens actuator based on the focus error signal obtained by the focus error detection circuit to follow the focal position of the light beam on the substrate surface or the information recording surface;
A surface shake tracking signal storage device that stores a surface shake tracking signal that is a drive signal applied to the objective lens actuator when the focus position is made to follow the base material surface;
A focus search drive signal generating circuit for generating a focus search drive signal which is a drive signal for changing the focal position of the light beam with respect to the optical disc;
A superimposed signal generation circuit that generates a signal in which the surface shake tracking signal stored in the surface shake tracking signal storage device and the focus search drive signal generated by the focus search drive signal generation circuit are superimposed;
A focus that draws focus on the information recording surface of the optical disc by controlling the objective lens actuator based on the superimposition signal generated by the superimposition signal generation circuit after the focus servo is drawn onto the substrate surface of the optical disc An optical disk apparatus comprising: a pull-in control circuit. The optical head device includes a light source that emits light beams of a plurality of wavelengths corresponding to reproduction on a plurality of types of optical disks, or a plurality of light sources that emit light beams having different wavelengths.
The focus pull-in control circuit uses the light beam having a focal length longer than the focal length of the objective lens in the light beam corresponding to the optical disc to be recorded / reproduced among the light beams of a plurality of wavelengths emitted from the light source. The optical disk apparatus according to claim 1, wherein a focus servo is pulled into the surface of the substrate of the optical disk. The optical head device includes a plurality of light sources that emit light beams having a plurality of wavelengths, a plurality of light sources that emit light beams having different wavelengths, and a plurality of objective lenses in correspondence with reproduction on a plurality of types of optical disks.
The focus pull-in control circuit is a light having a focal length longer than the focal length of the objective lens in the light source and objective lens used corresponding to the optical disk to be recorded / reproduced among the light source and objective lens emitting the plurality of light beams. The optical disk apparatus according to claim 1, wherein a focus servo is drawn onto a substrate surface of the optical disk using a combination of a light source that emits a beam and an objective lens.   4. The optical disc apparatus according to claim 2, wherein the light source that emits a light beam having a longer focal length of the objective lens is a light source that emits red light or infrared light.   5. The optical disc apparatus according to claim 2, wherein a focal length of the objective lens through which a light beam with a longer focal length of the objective lens passes is larger than a surface shake amount of the optical disc to be recorded and reproduced.   The focus pull-in control circuit pulls in the focus servo at a position where a focus shift due to spherical aberration corresponding to the substrate thickness of the optical disk is corrected in advance when the focus servo is pulled onto the substrate surface of the optical disk. The optical disc device according to any one of the preceding claims. A spherical aberration correction actuator for moving the collimator lens to correct the spherical aberration caused by the change in the substrate thickness of the optical disc;
The focus pull-in control circuit shifts the collimator lens to a correction position that is positioned when the thickness of the base material is the thinnest in advance when the focus servo is pulled into the base material surface of the optical disc. 2. An optical disk device according to item 1. An optical disc device according to any one of claims 1 to 7,
A computing device for computing information reproduced by the optical disc device;
An optical information device comprising: A focus pull-in control LSI provided in an optical disc apparatus that reproduces at least information by moving an objective lens by an objective lens actuator in a direction at least perpendicular to the optical disc to converge a light beam on the optical disc,
A focus error detection unit that generates a focus error signal in accordance with the positional deviation of the focal point of the light beam with respect to the substrate surface or the information recording surface of the optical disc;
A focus control unit that causes the focus position of the light beam to follow the surface of the base material or the information recording surface based on the focus error signal obtained by the focus error detection unit;
A surface shake follow-up signal storage unit that stores a surface shake follow-up signal that is a drive signal applied to the objective lens actuator when the focus position is made to follow the substrate surface;
A focus search drive signal generator for generating a focus search drive signal, which is a drive signal for changing the focal position of the light beam with respect to the optical disc;
A superimposition signal generation unit that generates a signal in which the surface shake tracking signal stored in the surface shake tracking signal storage unit and the focus search drive signal generated by the focus search drive signal generation unit are superimposed;
A focus pull-in control unit that pulls in the focus on the information recording surface of the optical disc based on the superimposition signal generated by the superimposition signal generation unit after the focus servo is pulled into the substrate surface of the optical disc. Focus pull-in control LSI characterized by

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